Angular speed responsive device



April 14, 1964 Filed NOV. 14, 1960 F. SAPHRA ANGULAR SPEED RESPONSIVEDEVICE 2 Sheets-Sheet 1 @y v y IN VEN TOR.

FREDER/CK SA PHRA MRR/VE Y Z April 14, 1964 F, SAPHRA 3,129,301

ANGULAR SPEED RESPONSIVE DEVICE Filed Nov. 14, 1960 2 Sheets-Sheet 2 AIRCRITICAL PRESSURE J`48 o SOURCE 73 y E/A/ INVENTOR. FEEDER/0K SA PH RATTR/VEY lllll? BY United States Patent C) 3,129,301 ANGULAR SPEEDRESPONSIVE DEVICE Frederick Saphra, Levittown, N.Y., assigner to SperryRand Corporation, Great Neck, NX., a corporation of Delaware Filed Nov.14, 1960, Ser. No. 68,895 1 Claim. (Cl. Zilli-80) This invention relatesto a device that is responsive to the angular speed of a rotating memberwherein the device provides little or no deflection with increasing loadup to a critical speed and at and beyond that speed provides anappreciable increase in the rate of deflection with slight increase inspeed. The present invention is particularly adaptable for use as aswitch or as a governor for rotating machinery.

It is particularly useful as a governor to maintain extremely preciseangular speed regulation of, for example, a gyroscopic rotor.Previously, this required a regulated power source which in the case ofan A.C. electrically driven rotor required a constant frequency powersupply and in the case of a pneumatically driven rotor necessitated aconstant pressure source. Regulated power sources of this type areextremely expensive to construct and in certain airborne applicationsthey are undesirably cumbersome and unduly heavy. Another known methodis to measure the gyro rotor speed against a xed frequency or angularspeed standard and when the speed limit determined by the standard isexceeded the power to the gyro rotor is cut ol. This necessitatesauxiliary equipment external to the gyro rotor which is unduly complexand unnecessarily heavy. Further, the prior art devices are relativelyinaccurate and subject to variations due to changes in the ambienttemperature.

The present invention overcomes the undesirable limitations of the priorart devices by providing a simple, compact angular speed responsivedevice which lits within the rotor itself. The device is completelyselfcontained and does not require any external adjustment or auxiliaryequipment. The device is extremely accurate and equally applicable toelectrically and pneumatically driven rotating machines.

It is an object of the present invention to provide a device responsiveto the angular speed of a rotating member which exhibits a low rate ofdeflection versus speed until a predetermined critical speed is reachedand thereafter an appreciable increase in the rate of deiiection isexhibited.

It is a further object of the present invention to provide aself-contained, extremely accurate, compact switch responsive to theangular speed of a rotating member which provides a switching action ata predetermined critical speed.

It is another object of the present invention to provide a simplegovernor device that is adapted for mounting within the rotating memberfor regulating the angular speed of said member.

The above objects are achieved by the present invention by means of adevice responsive to the angular speed of a rotating member comprising adeectable conditionally stable elastic column mounted for rotation withthe rotating member, the column being relatively long along itslongitudinal axis with respect to its cross-sectional area and having anonlinear elasticity characteristic whereby at a critical loadassociated with the critical angular speed of the member an appreciableincrease in the rate of deection versus load occurs and load-producingmeans rotating with the member for applying a load to the columnrepresentative of the angular speed of the member to thereby abruptlydeflect the column at the critical speed of the member.

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Referring now to the drawings,

FIG. 1 is a schematic View showing a column loaded in accordance withthe theory of the present invention;

FIG. 2 is a graph showing the load versus deection characteristic of thecolumn of FIG. l;

FIG. 3 is a top view of an electrically driven gyroscopic rotor having agovernor embodying the principle of the present invention adaptedthereto;

FIG. 4 is a sectional view of FIG. 3 taken along lines 4 4;

FIG. 5 is an electrical schematic wiring diagram of the embodiment ofthe invention shown in FIG. 3;

FIG. 6 is a partial sectional view of FIG. 3 taken along lines 6 6;

FIG. 7 is a perspective view partially in section of a pneumaticallydriven gyroscope that is governed by another embodiment of the presentinvention; and

FIG. 8 is a graph showing the load versus deflection characteristic ofthe column of FIG. 7.

The operation of the present invention is based upon Eulers theoryrelating to long columns. Referring to FIG. 1, in accordance with Eulerstheory, a long column 1b which is xed at one end 12 will fail bybuckling at a load L less than the elastic limit of the material of thecolumn I@ when the load L is applied in a direction along thelongitudinal axis 11 of the column 10. A sudden lateral deiiection, asindicated by the dotted line 13, will occur under some critical load andthe column 10 is then no longer in equilibrium. The column 10 is thusconditionally stable, i.e. stable below the critical load and unstableat and above the critical load.

By viewing FIG. 2 wherein the load L is plotted against the deiiectionthe abruptness of the rate of increase of deflection at the criticalload can be appreciated. A very sharp knee of the curve of FIG. 2 existswhen the critical or Euler load is reached. The sharpness of the kneedepends upon the general symmetry of the system; the greater thesymmetry, the sharper the knee. This extremely radical change of theload-deflection curve around the critical load with the deection ratebecoming extremely high after the critical load has been reached isutilized in the present invention to provide a sensitivity to smallchanges in speed at a predetermined critical speed.

The present invention will now be described with respect to a governorfor electrically and pneumatically driven gyroscopic rotors. It will beappreciated, however, that the present invention is equally adaptable tooperate as a device responsive to the angular speed of a rotating memberother than a gyroscopic rotor and as other than a governor.

Referring now to FIGS. 3 and 4, the angular speed responsive device 15of the present invention is mounted on the rim 16 of a gyroscopic rotor17. The rotor 17 is electrically rotated about its spin axis 18 by meansof an A.C. wound rotor induction motor, only the rotor windings 2@ ofwhich are shown for purposes of simplicity. The rotor windings 20 aredisposed within the rim 16 of the rotor 17.

The speed responsive device 15 comprises a convoluted, U-shaped, flatspring 21 having columns 22 and 23 therein, first and second weights ormasses 24 and 52, respectively, and an adjusting screw 26. Theextremities of the spring 21 are rigidly connected to the rim 16 of therotor 17 by means of screws 30 and 31 or other suitable fastening means.The spring 21 is relatively thin having a thickness in the order of .001inches and is constructed of resilient, conductive material such as heattreated beryllium copper, hardened spring stock, etc. The length of eachof the columns 22 and 23 is substantially greater than its respectivecross-sectional area thereby coming within the definition of a longcolumn in accordance with the aforementioned Eulers theory.

The masses 24 and 25 are attached on opposite sides of the base of theU-shaped spring 21 by screws or other suitable fastening means in such away that the centrifugal force exerted by the masses 24 and 25 isapplied to the ends of the columns 22 and 23 in a direction along theirrespective longitudinal axes 34 and 35. The base of the U-shaped spring21 is widened to accommodate the weights 24 and 25. For dynamicbalancing purposes, the rotor 17 has a portion thereof removed tocompensate for the added weight due to the device 15.

The adjusting screw 26 protrudes through the weights 24 and 25 and thespring 21 in order that one end thereof acts as one contact 36 of anelectrical switch 37. The other contact 38 of the switch 37 is mountedon the rotor windings 20, as shown more clearly in FIG. 5. One extremityof the rotor windings 2t) is connected to the contact 38 while the otherextremity thereof is connected to the rotor 17. The adjustment screw 26in its closed condition abutting against contact 38 completes a circuitfrom the rotor 17 through the windings 2t), the switch 37, the screw 26,the spring 21 and back to the rotor 17, all of the elements mentionedimmediately above being electrically conductive. As shown in FIG. 6, theadjustment `screw 26 also serves to predefiect the columns 22 and 23 tomaintain the switch 37 closed with a positive force.

With the device being utilized as a governor to maintain the rotor 17 ata predetermined constant angular speed, the device 15 is designed inorder that the centrifugal force due to the masses 24 and 25 at apredetermined or critical speed will apply a critical load to thecolumns 22 and 23 thereby causing them to abruptly and appreci'ablydeflect in accordance with the above mentioned Eulers theory.

In operation, with the switch 37 closed and below the critical speed,the current induced in the rotor windings 20 causes the gyro rotor 17 torotate about its axis 18. The .predeflection of the resilient columns 22and 23 by -means of the adjusting screw 26 holds the screw 26 firmlyagainst the contact 38 thereby maintaining the switch 37 closed andcompleting the electrical circuit through the windings to thereby causethe rotor 17 to continue to rotate. Y

At the critical speed, the centrifugal force applied by the masses 24and 25 to the ends of the columns 22 and -23 suddenly causes them tobuckle and deect as shown in dotted lines in FIG. 6. The sudden andappreciable deflection of the columns 22 quickly moves the adjustingscrew 26 away from the electrical contact 38 thereby opening the switch37 while simultaneously preventing undesirable arcing. By opening theswitch 37, the induced rotor current in the windings 20 is interruptedthereby eliminating the rotor driving torque. The rotor 17 loses itsangular speed until switch 37 is again closed by the spring action ofthe columns 22 and 23 when the rotor speed goes below the criticalspeed.

The present invention thus provides extreme accuracy in governing therotor 17 to precisely maintain a constant speed substantially equal tothe critical speed because the columns 22 and 23 are stable below thecritical speed but become elastically unstable when the sharp knee ofthe load versus deflection curve is reached at the critical speed. Thisaction provides appreciable deection of the columns 22 and 23 with onlya slight change in load thereby rapidly opening the switch V17 byquickly moving the screw 26 away from the contact 38 and for anappreciable distance which prevents arcing that would be detrimental tothe desired speed regulation. It will be appreciated therefore that theprecise speed regulation achieved by the present invention cannot beachieved by conven- Ational centrifugal force type governors becausewithout ,utilizing the principle explained above their response isinadequate to achieve the desired result.

A governor which operates on the same basic principle is shown appliedin FlG. 7 to a pneumatically driven director gyro dit. The gyro tti issupported in a conventional manner for movement around a vertical axisby means of a hollow outer gimbal 41 which is rotatably supported on achassis, not shown, byV means of spaced bearings i2 and 43. A hollowinner gimbal 44 is in turn rotatably supported about a horizontal axisby means of spaced air bearings 45 and 46 disposed on the outer gimbal41. The inner gimbal 4.4 in turn rotatably supports the rotor 5i) forrotation about its spin axis 51 by means of spaced air bearings 52 and53.

The rotor is a hollow, pneumatically driven, reaction-turbine-type rotorwhich is driven by means of air from an air pressure source d3. For easeof manufacturing, the rotor 50 is constructed of two parts that arebolted or otherwise fastened to each other in a conventional manner notshown. The air pressure source 48 is connected to provide air throughconduits in the hollow bearing 42, the hollow outer gimbal 41, the airbearings 45 and 46, the hollow inner gimbal 4A, the air bearings 52 and53 to a centrally disposed inner cavity 54 within the hollow rotor 5t).The rotor 55 further includes a reaction nozzle 55 connected by means ofa conduit 56 to the cavity 54.

The governor of the present invention is also disposed within the cavity54. The governor 60 comprises a thin, ilat, elastic column 61 having alongitudinal axis 62, a weight or mass 63 which also serves as athrottling valve in a manner to be described, and a set screw 65 andassociated helical biasing spring 66. In this embodiment of the presentinvention, the column 61 is a long column in accordance with theaforementioned Euler theory and it is diametrically disposed within thecavity 54. The column 61k is pre-buckled a predetermined amount by meansof the set screw 65 which is screwed to the rotor Sti and bears againsta spring 66 which in turn abuts against one end of the column 61 toapply a preload in a direction along the axis 62. The other end of thecolumn 61 is constrained in a slot 67 in the rotor Sti.

The mass 63 is disposed with its longitudinal axis 70 perpendicular tothe longitudinal axis 62 of the column 61. The lower portion of the mass63 is in the form of a rod 71 which has its lower extremity fastened tothe center of the bowed column 61. The mass 63 in addition to serving asa weight also has an enlarged central portion 72 which cooperates with amatching portion 73 of the conduit 56 to operate as a poppet orthrottling valve. The upper portion 74 of the mass 63 is iluted topermit the passage of air through the conduit 56 when the poppet valveportion 72 is not closed.

In order to provide proportional control of the air ow through thenozzle 55 instead of the on-oif action o-f the switch 37 of theembodiment of the invention of FIGS. 3 and 4, the column 61 has a loadversus deection characteristic as shown in FiG. 8. This providesproportional control and thus extremely precise angular speed regulationof the rotor V50 in la manner to be described. The mass 63 is designedto provide a centrifugal force which results in an extremely high rateof deection versus lload when the critical load is reached at thedesired or critical speed.

In operation, when the gyro 40 is started, the high pressure air fromthe source 48 is provided through the conduits to the cavity 54 andthence through the fluted portion 74 of the mass 63 and the conduit 56to the reaction nozzle 55 where it produces a reaction force on therotor 50 causing it to spin about its axis 51 in a counterclockwisedirection as indicated by the arrow.

As the rotor 50l approaches its desired or critical angulai speed, themass 63 will, due to centrifugal faction, apply a force radially in anoutward direction along thel axis 71 which will be transmitted to theattached column 61. The column 61 will deflect as a result of this loadin accordance with the graph of FIG. 8 thereby causing the poppet valveportion 72. of the mass 63 to begin to throttle the air through theconduit 56 and thus the nozzle 55.

At and above the critical speed, the load applied by the mass l63A iscritical and the rate of deilection versus load is a maximum therebyclosing off the air supply to the nozzle 5S causing the rotor 50 to slowdown. As the angular speed of the rotor 50 goes below the criticalspeed, the valve 72 again opens in accordance with the graph of FIG. 8and permits air to flow through the nozZ-le `55 thereby causing therotor 50 to increase its speed. The speed regulation is extremely tinein the region in which the velocity of the rotor has to be governedsince the throttling eiect in this embodiment of the invention iscontinuous and proportional instead of on-olf.

It will be appreciated that both embodiments of the invention rely onthe non-linear behavior of conditionally stable elastic columns and takeadvantage of the very large increase of deflection with little or noincrease in `load once the range of critical stability has been reached.The present invention provides extremely accurate speed regulation inspite of wide variation in the frequency and/ or voltage of theelectrical source or the pressure of the pressure iluid source.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words of`description rather than of limitation and that changes within thepurview of the appended claim may be made without departing from thetrue scope and spirit 'of the invention in its broader aspects.

What is claimed is:

An angular speed responsive switch comprising a rotating member havingan axis `of rotation comprising a dellectable conditionally stableelastic column mounted for rotation with said rotating member, saidcolumn being relatively long along its longitudinal axis with respect toits cross-sectional area and having a non-linear elasticitycharacteristic whereby lat a critical load associated with a criticalangular speed of said member an appreciable increase in the rate ofdeection versus load occurs, said longitudinal axis being disposedsubstantially in .a plane perpendicular to said axis of rotation,load-producing means rotating with said member and `etfectivelyconnected to an extremity of said col-umn `for applying a compressiveload to said column in the direction of said longitudinal axisrepresentative of the angular speed of said member to thereby abruptly`deilect said Column at said critical speed of said member, saidloadproducing means being disposed to move substantially parallel Ywithrespect to said axis of rotation, and switch means having one contactmounted on said rotating member and another contact mounted on saidcolumn whereby below said critical speed said contacts abut and abovesaid critical speed said contacts are spaced, in the latter case due tothe abrupt :deflection of said column.

References Cited in the file of this patent UNITED STATES PATENTS Re.20,993 Groot Ian. 31, 1939 1,025,618 Fish May 7, 1912 1,781,610 TorokNov. 11, 1930 1,984,512 Anderson Dec. 18, 1934 2,503,950 Johnson Apr.11, 1950 2,691,516 Fischer Oct. 12, `1954 2,779,582 Hopper et al. Ian.29, 1957 2,903,535 Sparklin Sept. 8, 1959 2,938,974 Querfurth May 31,1960

